Thermal processing torches, such as plasma arc torches, are widely used in the heating, cutting, gouging and marking of materials. A plasma arc torch generally includes an electrode, a nozzle having a central exit orifice mounted within a torch body, electrical connections, passages for cooling, and passages for arc control fluids (e.g., plasma gas). Optionally, a swirl ring is employed to control fluid flow patterns in the plasma chamber formed between the electrode and the nozzle. In some torches, a retaining cap can be used to maintain the nozzle and/or swirl ring in the plasma arc torch. In operation, the torch produces a plasma arc, which is a constricted jet of an ionized gas with high temperature and sufficient momentum to assist with removal of molten metal.
Gouging of conductive (e.g., metallic) materials is often needed for a number of material processing applications and products. These gouges typically form troughs/channels in the workpiece by removing materials to a certain desired depth. A gouging process can also be used to remove welds that contain known process defects or fractures. In today's gouging operations with typical plasma arc torches having a circular bore, the width of a gouge is limited by plasma processing, such as by standoff, amperage, and process speed. Thus, to make a wider gouge, a traditional plasma arc torch needs to pass over a workpiece a number of times, essentially forming a series of connected channels with similar depth. Further, some operators and systems oscillate the torch during gouge processing to widen the affected area while maintaining depth control. However, repeated torch passing and/or torch oscillation are like to produce inconsistent surface textures (e.g., scalloped and/or ribbed features), require skilled operators and/or complex machinery to achieve, and be time consuming. Even though automated torch oscillation may minimize surface texture variations, it greatly increases processing time because high oscillation to low linear travel speed ratio is often needed to avoid the variations.
Therefore, there is a need to design torches and torch consumables that can produce a wide gouge profile in the workpiece (e.g., the width substantially greater than the depth) during a single pass of the torch over the workpiece and/or without torch oscillation.